Update pom.xml to use sl4j-api 1.7.5

This change will update Model-Citizen to use slf4j-api version 1.7.5 over slf4j-api 1.6.1.

This change is due in part to the following exception being thrown:

java.lang.NoSuchMethodError: ch.qos.logback.classic.LoggerContext.getBithTime()

Upon further investigation I found the following:

## January 25th, 2011 - Release of version 0.9.28
### Breaking change: In the Context interface, the previously misspelled property bithTime is now renamed as birthTime.

In the Context interface, the previously misspelled property bithTime is now renamed as birthTime. This is a backward-incompatible change. All pre-existing references to "bithTime" property now need to referenced as "birthTime".


Tests passed locally.